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Distribution of coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments from canals and coastal waters of Venice, Italy
0146-6380/88 $3.00+ 0.00 Copyright © 1988 Pergamon Press plc
Advances in Organic Geochemistry 1987
Org. Geochem. Vol. 13, Nos 4-6, pp. 757-763, 1988
Printed in Great Britain. All rights reserved
Distribution of coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments from canals and coastal waters of Venice, Italy E. S. VAN VLEET 1., V. U. FOSSATO2, M. R. SnERWtN~, H. B. LOVETT1 and F. DOLCI 2 ~Department of Marine Science, University of South Florida, 140 Seventh Avenue South, St Petersburg, FL 33701, U.S.A. 2Istituto di Biologia del Mare, Riva 7 Martiri 1364/A, 30122 Venezia, Italia Al~tract--In order to evaluate the degree of organic pollution in canals and surrounding coastal waters of Venice, Italy, fecal sterols, petroleum hydrocarbons and chlorinated hydrocarbons were analyzed in twenty-five sediment samples collected from Venetian canals, the surrounding Veneto Lagoon, the industrialized area of Porto Marghera, and the Northern Adriatic Sea. Although the main Venetian canals are at least partially flushed by tides, most canals still have mud bottoms which are ideal for preservation of chemical pollutants. The fecal sterol, coprostanol, was analyzed to evaluate the accumulation and dispersal of untreated waste from the city of Venice. Coprostanol "hotspots" gave indications of where health hazards may exist for local populations. Petroleum hydrocarbon contamination was observed in essentially all areas except the Northern Adriatic. Highest hydrocarbon concentrations were found near Porto Marghera followed by decreasing concentrations in the Venetian Canals and Veneto Lagoon. Based upon alkylated homolog distributions of polycyclic aromatic hydrocarbons, fossil fuel combustion appears to be the major source of these hydrocarbons. Chlorinated hydrocarbons were present in a wide range of concentrations. The spatial distribution of these compounds (HCB, HCH, DDT, and PCB) could be clearly correlated with local inputs. Key words: pollution, hydrocarbons, pesticides, PCB's, coprostanol, Venice, sediments
INTRODUCTION The city of Venice, Italy lies in the Lagoon of Venice (Laguna Veneta) which is connected to the Northern Adriatic Sea through the port entrances of Lido, Malamocco, and Chioggia. For several hundred years, the city and the lagoon have undergone dramatic configurational and compositional changes due to man's influence. The lagoon serves as the drainage basin for about 200,000 hectares having a population base of about 1.3 million persons (Ghetti and Batisse, 1983). As a result, many contaminants and waste products are washed into the lagoon. Municipal wastes have long been discharged directly into Laguna Veneta. Although sewage treatment plants have recently been built to serve the coastal cities of Mestre, Chioggia and Iesolo, Venice still has no sewage treatment facilities. Raw sewage and its associated pathogenic and toxic components are still being discharged directly into Venice's canals and coastal waters. In addition, the Lagoon of Venice is one of the main oil harbors in Italy. Porto Marghera, adjacent to Venice, contains many sizable storage facilities where oil tankers offload their cargo. Significant amounts of petroleum may be lost to the environment as a result of these activities. Many associated chemical industries have arisen around Porto Marghera and may contribute contaminants to
*Author to whom correspondence should be addressed.
the lagoon in their industrial effluents. The Lagoon of Venice is also surrounded by significant agricultural activity which may contribute nutrients, fertilizers and pesticides to the lagoon via runoff. The environmental health of the lagoon greatly depends upon maintaining adequate tidal flushing to prevent the build-up of contaminants in the water, sediments and organisms. Over the past few decades, little attention has been paid to the maintenance of interior canals of the city, which has resulted in inadequate tidal flushing and an accumulation of a deep layer of recent sediments. Due to recent increases in relative mean sea level height and tidal storm surges, the city of Venice has experienced dramatic, and sometimes devastating flooding of the city (Ghetti and Batisse, 1983). A plan has recently been adopted to construct flood gates in the three channel entrances which would be raised during extremely high tides or storm surges to prevent flooding. However, altering the tidal flushing pattern may also have a long term effect on the build-up of pollutants in the canals and coastal waters of Venice. Several individuals studies have investigated the distribution of petroleum hydrocarbons (Fossato and Siviero, 1974; Fossato and Dolci, 1976) and chlorinated hydrocarbons (Fossato and Craboledda, 1979; Fossato, 1982; Nasci and Fossato, 1982; Donazzolo et al., 1983) in sediments and organisms from the Lagoon of Venice. Few studies, however, have investigated the co-occurrence of several types of contaminants in the same suite of samples collected 757
758
E.S. VAN VLEET et al.
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Fig. 1. (A) Sampling stations, (B) Total hydrocarbons O~gtg), (C) Coprostanol (#g/g), and (D) Coprostanol (% of total sterols) in sediments of the canals and lagoon of Venice. Italy.
in this area. The present study was undertaken to investigate the current state of health of sediments and organisms from the canals and Lagoon of Venice based upon a survey of several different types of pollutants including petroleum hydrocarbons, pesticides, polychlorinated biphenyls, and coprostanol, a fecal sterol indicative of sewage discharge.
METHODS Surface sediments (top 5 cm) were collected from 25 stations in the canals, lagoon, and coastal waters of Venice, Italy during September and October, 1985 (Fig. !). [Mussels (Mytilus gallprovincialis) were also collected and similarly analyzed from 20 of these
Coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments
759
Table 1. Data for organic and inorganic parameters measured in sediments from the canals and lagoon of Venice, Italy Station 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
% H 2 0 %CO 3 %OC 29.6 39.9 50.8 55.8 41.9 30.5 42.9 31.3 38.0 22.1 37.8 25.2 25.9 31.7 46.7 37.6 30.2 48.0 50.1 18.3 49.9 52.5 44.8 51.7 47.2
56.5 51.7 44.7 47.8 52.4 54.9 55.0 48.6 52.5 68.3 55.8 63.5 61.2 50.7 48.3 45.8 48.0 43.2 37.0 64.0 39.6 48.7 33.6 42.7 36.2
0.9 2.2 2.9 2.0 1.4 1.3 1.6 1.1 1.3 0.3 1.4 0.6 0.5 1.3 2.0 2.2 0.7 2.1 2.3 0.1 2.0 3.3 3.3 3.1 4.6
XCOP (/zg/g)
%COP
EHC (/*gig)
EPCB (ng/g)
Y-DDT (ng/g)
1.7 10.4 2.2 3.6 0.9 1.0 1.5 2.2 2.8 1.0 2.8 0.8 1.7 2.9 3.1 8.7 0.5 1.8 2.3 0.2 0.3 40.9 13.6 20.5 4.4
18 33 13 15 8 10 9 16 15 19 15 7 14 15 22 28 7 11 8 10 5 39 42 38 29
84 129 138 78 28 93 39 48 27 6 68 14 64 35 90 250 5 40 89 3 228 302 115 66 391
128 41 259 49 140 744 55 306 119 113 277 12 20 190 187 230 9 41 297 5 152 305 350 292 448
16 4 19 4 5 105 5 32 10 3 66 2 3 22 12 21 1 3 6 2 8 28 120 69 79
EHCH (ng/g)
I;HCB (ng/g)
0.3 <0.1 0.3 0.1 0.2 0.2 0.4 0.1 0.1 <0.1 0.8 0.3 0.7 2.1 0.6 2.1 0.1 0.3 0.8 0.2 0.8 0.1 <0.1 0.1 0.5
1.9 0.9 3.5 6.5 4.0 2.8 1.2 1.0 0.7 0.1 0.8 0.1 0.2 0.8 2.8 1.9 2.4 13.0 224.0 0.2 66.0 3.5 2.7 7.8 3.4
Abbreviations: %CO 3 = percent total carbonates, %OC = percent organic carbon, ECOP = total coprostanol, %COP = coprostanol as percentage of total sterols, ~ H C = total hydrocarbons, ZPCB = total polychlorinated biphenyls, ' r D D T = total DDT's, ~ H C H = total hexachlorocyclohexane, XHCB = total hexachlorobenzene.
stations. These results are being reported elsewhere.] After addition of internal standards (5~-androstane, o-terphenyl, and 5~-androstanol), approximately 20g (dry weight) of each sediment was Soxhlet extracted and saponified using 2:1 0.5N Methanolic KOH:benzene (Van Vleet et al., 1986). Extracts were dried over anhydrous sodium sulfate, evaporated under vacuum to -~ 1 ml, and processed by silica gel-alumina column chromatography (Reinhardt and Van Vleet, 1986) to isolate the saturated (aliphatic; F1) hydrocarbons, unsaturated (aromatic; F2) hydrocarbons, and total sterols (F3). Individual column eluates were analyzed by high resolution gas chromatography (Hewlett-Packard 5580A GC) using a 30 m DB-5 fused silica column with hydrogen as a carrier gas. Oven temperature programming conditions were as follows: hydrocarbons (FI and F2)--100-280°C at 6°Cmin-~; sterols--180-280°C at 3°C min-1. Individual compounds were corrected for detector response factors and integrated using a Hewlett-Packard data processor. Structural confirmation and polycyclic aromatic hydrocarbon (PAH) homolog distributions were determined by combined high resolution gas chromatography-mass spectrometry (GCMS) using a Hewlett-Packard 5992B-GCMS system under conditions similar to those employed by GC. Extraction of chlorinated hydrocarbons was accomplished by refluxing ~- 50 g of wet sediment in a Soxhlet apparatus for 8 h firstly with acetonitrile then with hexane, using 2,4,5-trichloro-biphenyl as an internal standard. Combined extracts were partitioned against pesticide-free water and the aqueous phase was extracted twice more with 50 ml portions O.G. 13/4-6--M
of hexane. Combined extracts were dried over anhydrous sodium sulfate, evaporated under vacuum to I ml, shaken with concentrated sulfuric acid to remove co-extracted substances (Murphy, 1972), and then shaken with mercury to bind sulfur compounds which interfere in the GC analysis. Extracts were fractioned into classes of chlorinated hydrocarbons by elution from a silica gel micro-column (Palmork and Villeneuve, 1980) and concentrated to I ml for gas chromatographic analysis using a Carlo Erba FV2351 electron capture GC. Identity of organochlorines was determined from their retention times on two GLC columns (2 m x 4 mm i.d.; 5% DC 200 on Gas Chrom Q BW-DMCS and 5% QF-I on Chromosorb W AW-DMCS). Quantification was based on peak-height measurement and comparison to responses of reference standards (HCB, HCH, DDT's, and Aroclors 1254 and 1260). Organic carbon was analyzed by the chromate digestion method of FAO (1975). Total carbonates (CaCO3 + MgCO3) were measured by a gas-volumetric method in which the volume of CO2 released from 1 g of sediment upon acidification with 25 ml of 1.2 N HCI is measured manometrically and compared to standard CaCO3 gas release curves. Moisture content was determined after drying a weighed subsample of each sediment to constant weight at 65°C. RESULTS AND DISCUSSION
Data obtained from all organic carbon, carbonate, and lipid analyses are reported in Table 1 and plotted in Figs 1 and 2. Organic carbon values in the lagoon
760
E.S. VAN VLEETet
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A
(?C ; ~ I
,°:1°oo I =:70:001" l
Fig. 2. (A) Total DDT, (B) Total PCB's, (C) HCB, and (D) HCH in sediments of the canals and lagoon of Venice, Italy. All concentrations are in ng/g. range from 0.3 to 4.6% with highest values ( > 3 % ) being observed in the interior canals of the city (Sta. 22-25) and the lowest value being observed at the control station (Sta. 20) located = 14 km outside of the lagoon in the Northern Adriatic Sea. Most other organic carbon values in the lagoon ranged from about 0.3-2.9% and were inversely correlated with carbonate contents of the sediments (correlation
coefficient r = -0.81, Table 2). Unusually high accumulation of organic carbon was not observed in this area. The fecal sterol, coprostanol (5fl-cholestan-3fl-ol), has been used in many studies to investigate sewage discharge (Hatcher and McGillivary, 1979; Boehm, 1983; Pierce and Brown, 1984; Sherwin, 1988; and many others). Since coprostanol is produced almost
Coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments
761
Table 2. Correlationeoeflicients(r) among organic and inorganicparametersmeasured in the present study %H20 %C03 %OC HC PCB DDT HCH HCB COP %COP %H20 1.00 %CO3 -0.77 1.00 %OC 0.81 -0.81 1.00 HC 0.50 -0.55 0.78 1.00 PCB 0.21 -0.38 0.47 0.45 1.00 DDT 0.15 -0.39 0.49 0.33 0.82 1.00 HCH -0.05 -0.12 0.01 0.22 0.05 -0.07 1.00 HCB 0.30 -0.40 0.14 0.07 0.12 -0.14 0.15 1.00 COP 0.42 -0.26 0.54 0.48 0.23 0.27 -0.13 -0.09 1.00 %COP 0.31 -0.34 0.63 0.48 0.29 0.51 -0.08 -0.24 0.77 1.00 Abbreviationsas in Table 1.
exclusively in the intestines of mammals (including man) by enteric reduction of cholesterol, the presence of coprostanol is considered to be a reliable indicator of municipal waste discharge. Figures 1C and 1D show the sedimentary concentrations of coprostanol (rig/g) and the abundance of coprostanol as percent of total sterols. In areas with the highest concentrations of coprostanol, this compound generally makes up a greater percentage of total sterols (r = 0.77, Table 2). These areas most commonly represent interior canals with limited water circulation and tidal flushing. Coprostanol concentrations range from 0.2 #g/g at the Northern Adriatic station (Sta. 20) to 40.9/~g/g in the interior canals. Away from the interior canals, coprostanol concentrations averaged 1.8 + 1.0/~g/g (n = 18) while interior canals averaged 16.4 _ 13.1/zg/g (n = 6). While coprostanol concentrations in areas away from interior canals are comparable to many other estuaries around the world, concentrations in the interior canals are up to an order of magnitude higher than most other areas (Goodfellow et al., 1977; Hatcher and McGillivary, 1979; Escalona et al., 1980; Sherwin, 1988). High coprostanol concentrations in these canals provide an indicator of potential public health problems associated with other contaminants (such as pathogenic bacteria, etc.) resulting from raw sewage discharge. Sedimentary hydrocarbon concentrations ranged from 2.7/~g/g in the Northern Adriatic to 391/~g/g in the interior canals (Table 1, Fig. 1B). Although high concentrations were more widespread than for coprostanol, hydrocarbon contamination was only weakly correlated with coprostanol concentrations (r = 0.48, Table 2). Nonetheless, Fig. 1 shows that "hotspots" for hydrocarbons and coprostanol occur in the same general vicinities. Hydrocarbons are also concentrated around the industrial zone of Porto Marghera. Stations taken in interior canals and at Porto Marghera averaged 196_ 115 #g/g (n = 8) while other areas of the lagoon averaged 50 + 36/~ g/g (n = 16). Although gas chromatograms from most areas contained 70-80% unresolved hydrocarbon components, the F1 resolved peaks did not directly resemble petroleum inputs. Resolved alkanes showed significant contributions from nCl7-nC2! and nC25-nC3! with slight odd carbon predominances (Table l). F2 (aromatic) hydrocarbon fractions, how-
ever, were strongly dominated by unsubstituted PAH components, specifically by fluoranthene, pyrene, phenanthrene and benz(a)anthracene/chrysene (the latter two were not individually quantititated). In general, the ratio of the unsubstituted parent PAH compound to the total C1423 alkylated homologs was >1. Based upon the high percentage of unresolved components, low continuous n-alkane abundance, and dominance of unsubstituted PAH homologs in the F2 fraction, we suggest that hydrocarbons in both canal and lagoon sediments result from significantly degraded products of fossil fuel combustion rather than direct petroleum input. Since the city of Venice primarily uses natural gas for home heating fuel (Getti and Batisse, 1983), sedimentary hydrocarbons are more likely to result from inefficient burning of fuel oils by the extensive boat traffic in the Lagoon or by the industries in Porto Marghera. Hydrocarbon concentrations are well correlated with total organic carbon contents (r = 0.78, Table 2) in the sediments, indicating that sedimentary hydrocarbon distributions may also reflect extensive microbial reworking of organic matter discharged directly to the canals and lagoon. Fossato and coworkers (Fossato and Sivero, 1974; Fossato and Dolci, 1976, 1977; Fossato et al., 1979) have analyzed mussels from the Lagoon of Venice and have attributed hydrocarbon accumulation in the mussels to petroleum inputs. In the present study, hydrocarbons extracted from mussels much more clearly resembled direct petroleum inputs (n-alkanes continuous with odd/even ratio ~- 1.0) than did the sedimentary hydrocarbons. This observation suggests that petroleum contaminants in the lagoon may be taken up by mussels, but are probably degraded or carried away by tidal flushing prior to being permanently deposited in the sediments. Chlorinated hydrocarbons that were analyzed in the sediments included total DDT (dichlorodiphenyltrichloroethane), total PCB's (polycholorinated biphenyls), HCH (hexachlorocyclohexane), and HCB (hexachlorobenzene). For decades, PCB's and HCB have been used for a variety of industrial applications while DDT and HCH have been used as pesticides and fungicides in agriculture. Since 1970, the use of HCH has been greatly limited in Italy and by 1978 its use was completely banned by Italian regulations. At
762
E.S. VAN VLEETet al.
the same time, the use of PCB's was restricted to non-dispersive systems. These highly toxic compounds are extremely resistant to chemical and biological degradation and may persist in the environment for several decades. Table 1 and Fig. 2 show the concentrations and distributions of these components around the city and lagoon of Venice. Distribution patterns for the various chlorinated hydrocarbons differ and are dependent upon varying local inputs. Total DDT and PCB's show distribution patterns similar to coprostanol and total hydrocarbons, being concentrated mainly in sediments of the interior canals. High PCB concentrations appear to be much more widespread and are also found at Porto Marghera. For PCB's and DDT's, an area of relatively high concentration was also observed at Sta. 6 near the island of Giudecca, and was probably due to the former presence of a shipyard in this area. Total DDT/total PCB concentration ratios are <0.5 at all stations, and are similar to values reported earlier for DDT and PCB's in mussels and sediments collected in other areas of the lagoon (Fossato and Craboledda, 1979; Fossato, 1982). Although this may indicate a higher input of PCB's to the environment, it may also reflect different biochemical pathways of these compounds in the lagoon. Although DDT and PCB concentrations are strongly correlated with each other (r = 0.82, Table 2), they are only weakly correlated with hydrocarbon or coprostanol concentrations (r =0.23-0.45). Nonetheless, distribution patterns are basically similar for all of these compounds. Distribution patterns of HCB and HCH are strikingly different than for the other compounds (Fig. 2). Interior canals appear to have relatively low concentrations compared with some of the other areas. HCB is concentrated primarily near Porto Marghera and may be associated with release by the chemical industry in this area. HCH shows relatively high concentrations near the northern portion of Venice and probably reflects agricultural inputs, although the exact source is unknown. Table 2 confirms that HCH and HCB are very poorly correlated with any of the other organic parameters measured (r = 0.01-0.19). In summary, we can see that "hotspots" for hydrocarbons, fecal sterols, and chlorinated hydrocarbons occur primarily in interior canals of Venice and the industrial area of Porto Marghera. Although these "hotspots" show elevated concentrations relative to other areas of the Lagoon, concentrations are not necessarily higher than in other coastal bays and estuaries around the world. An exception is the fecal sterol, coprostanol, which shows up to an order of magnitude higher concentration relative to sediments from most other marine environments. These high concentrations result primarily from the input of untreated waste into the interior canals of Venice. It appears that flushing of the canals and lagoon by
tidal currents limits the accumulation of pollutants in most areas studied, although dredging of the interior canals would significantly reduce pollutant concentrations in these areas. If flood gates are constructed that restrict tidal circulation in the lagoon, accumulation of pollutants could dramatically increase. Acknowledgements--Financial support was provided by the
Gladys Krieble Delmas Foundation. Investigators from the University of South Florida greatly appreciate the hospitality and assistance provided by the Istituto di Biologia del Mare in Venice. REFERENCES
Boehm P. D. (I 983) Coupling of participate organic pollutants between the estuary and water column in the New York Bight region. Can. J. Fish. Aquat. Sci. 40, 262-276. Donazzolo R., Vitturi L. M., Orio A. A. and Pavoni B. (1983) DDT and PCB's in sediments of the Venice Gulf. Environ. Technol. Lett. 4, 451-462. Escalona R. L., Rosales M. T. L. and Mandelli E. F. 0980) On the presence of fecal steroids in sediments from two Mexican harbors. Bull. Environ. Contain. Toxicol. 24, 289-295. FAO (1975) Manual of Methods in Aquatic Environment Research. FAO Fisheries Technical Paper No. 137. Food and Agricultural Organization of the United Nations. Rome. Fossato V. U. (1982) Etude des hydrocarbures chlores dans l'environement de la lagune de Venise. In VI e" Journees Etud. Pollutions, pp. 465-468. Commission Internationale pour l'Exploration Scientifique de la Mer Mediterranee. Monaco. Fossato V. U. and Siviero E. (1974) Oil pollution monitoring in the Lagoon of Venice using the mussel Mytilus galloprovincialis. Mar. Biol. 25, 1--6.
Fossato V. U. and Dolci F. (1976) Inquinamento da idrocarburi nel bacino settentrionale della laguna Veneta. Archo. Oceanogr. Limnol. 18, 73-82. Fossato V. U. and Craboledda L. (1979) Chlorinated hydrocarbons in mussels, Mytilus sp., from the Laguna Veneta. Archo. Oceanogr. Limnol. 19, 169-178. Fossato V. U., Nasci C. and Dolci F. (1979) 3,4-Benzopyrene and perylene in mussels, Mytilus sp. from the Laguna Veneta, Northeast Italy. Mar. Environ. Res. 2, 47-53. Ghetti A. and Batisse M. (1983) The overall protection of Venice and its lagoon. Nature and Resources 19, 7-19. Goodfellow R. M., Cardoso J., Eglinton G., Dawson J. P. and Best G. A. (1977) A fecal sterol survey in the Clyde estuary. Mar. Pollut. Buff. 8, 272-276. Hatcher P. G. and McGillivary P. A. (1979) Sewage contamination in the New York Bight. Coprostanol as an indicator. Environ. Sci. Technol. 13, 1225-1229. Murphy P. G. 0972) Sulfuric acid for the cleanup of animal tissues for analysis of acid-stable chlorinated hydrocarbon residues. J. Assoc. Official Agricultural Chemist 55, 1360-1362. Nasci C. and Fossato V. U. (I982) Studies on physiology of mussels and their ability in accumulating hydrocarbons and chlorinated hydrocarbons. Environ. Technol. Left. 3, 273-280. Palmork K. H. and Villeneuve J. P. (1980) Outline of the method to be used for the determination of chlorinated hydrocarbons in seawater. In Workshop on the Intercalibration of Sampling Procedures of the IOC/WMO/UNEP Pilot Project on Monitoring Background Levels of Selected Pollutants in Open-Ocean Waters, Bermuda, 11-26 January 1980. IOC/UNESCO Workshop Report No. 25, pp. 25-55. Pierce R. H. and Brown R. C. (1984) Coprostanol distribu-
Coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments tion from sewage discharge into Sarasota Bay, Florida. Bull. Environ. Contain. Toxicol. 32, 75-79. Reinhardt S. B. and Van Vleet E. S. (1986) Lipid composition of twenty-two species of Antarctic midwater zooplankton and fish. Mar. Biol. 91, 149-159. Sherwin M. R. (1988) Sterols as Source Indicators for
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Organic Matter in Tampa Bay Sediments. M.S. thesis, University of South Florida. Van Vleet E. S., 3oyce R. M. and Sherwin M. R. (1986). Comparison of anthropogenic hydrocarbon inputs to two subtropical marine estuaries. Sci. Total Environ. 56, 221-230.
Advances in Organic Geochemistry 1987
Org. Geochem. Vol. 13, Nos 4-6, pp. 757-763, 1988
Printed in Great Britain. All rights reserved
Distribution of coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments from canals and coastal waters of Venice, Italy E. S. VAN VLEET 1., V. U. FOSSATO2, M. R. SnERWtN~, H. B. LOVETT1 and F. DOLCI 2 ~Department of Marine Science, University of South Florida, 140 Seventh Avenue South, St Petersburg, FL 33701, U.S.A. 2Istituto di Biologia del Mare, Riva 7 Martiri 1364/A, 30122 Venezia, Italia Al~tract--In order to evaluate the degree of organic pollution in canals and surrounding coastal waters of Venice, Italy, fecal sterols, petroleum hydrocarbons and chlorinated hydrocarbons were analyzed in twenty-five sediment samples collected from Venetian canals, the surrounding Veneto Lagoon, the industrialized area of Porto Marghera, and the Northern Adriatic Sea. Although the main Venetian canals are at least partially flushed by tides, most canals still have mud bottoms which are ideal for preservation of chemical pollutants. The fecal sterol, coprostanol, was analyzed to evaluate the accumulation and dispersal of untreated waste from the city of Venice. Coprostanol "hotspots" gave indications of where health hazards may exist for local populations. Petroleum hydrocarbon contamination was observed in essentially all areas except the Northern Adriatic. Highest hydrocarbon concentrations were found near Porto Marghera followed by decreasing concentrations in the Venetian Canals and Veneto Lagoon. Based upon alkylated homolog distributions of polycyclic aromatic hydrocarbons, fossil fuel combustion appears to be the major source of these hydrocarbons. Chlorinated hydrocarbons were present in a wide range of concentrations. The spatial distribution of these compounds (HCB, HCH, DDT, and PCB) could be clearly correlated with local inputs. Key words: pollution, hydrocarbons, pesticides, PCB's, coprostanol, Venice, sediments
INTRODUCTION The city of Venice, Italy lies in the Lagoon of Venice (Laguna Veneta) which is connected to the Northern Adriatic Sea through the port entrances of Lido, Malamocco, and Chioggia. For several hundred years, the city and the lagoon have undergone dramatic configurational and compositional changes due to man's influence. The lagoon serves as the drainage basin for about 200,000 hectares having a population base of about 1.3 million persons (Ghetti and Batisse, 1983). As a result, many contaminants and waste products are washed into the lagoon. Municipal wastes have long been discharged directly into Laguna Veneta. Although sewage treatment plants have recently been built to serve the coastal cities of Mestre, Chioggia and Iesolo, Venice still has no sewage treatment facilities. Raw sewage and its associated pathogenic and toxic components are still being discharged directly into Venice's canals and coastal waters. In addition, the Lagoon of Venice is one of the main oil harbors in Italy. Porto Marghera, adjacent to Venice, contains many sizable storage facilities where oil tankers offload their cargo. Significant amounts of petroleum may be lost to the environment as a result of these activities. Many associated chemical industries have arisen around Porto Marghera and may contribute contaminants to
*Author to whom correspondence should be addressed.
the lagoon in their industrial effluents. The Lagoon of Venice is also surrounded by significant agricultural activity which may contribute nutrients, fertilizers and pesticides to the lagoon via runoff. The environmental health of the lagoon greatly depends upon maintaining adequate tidal flushing to prevent the build-up of contaminants in the water, sediments and organisms. Over the past few decades, little attention has been paid to the maintenance of interior canals of the city, which has resulted in inadequate tidal flushing and an accumulation of a deep layer of recent sediments. Due to recent increases in relative mean sea level height and tidal storm surges, the city of Venice has experienced dramatic, and sometimes devastating flooding of the city (Ghetti and Batisse, 1983). A plan has recently been adopted to construct flood gates in the three channel entrances which would be raised during extremely high tides or storm surges to prevent flooding. However, altering the tidal flushing pattern may also have a long term effect on the build-up of pollutants in the canals and coastal waters of Venice. Several individuals studies have investigated the distribution of petroleum hydrocarbons (Fossato and Siviero, 1974; Fossato and Dolci, 1976) and chlorinated hydrocarbons (Fossato and Craboledda, 1979; Fossato, 1982; Nasci and Fossato, 1982; Donazzolo et al., 1983) in sediments and organisms from the Lagoon of Venice. Few studies, however, have investigated the co-occurrence of several types of contaminants in the same suite of samples collected 757
758
E.S. VAN VLEET et al.
Uf. ,X
0114 k
i i
m
//
L_s'd_____J(__
B
I 0 o-, o°,,,,il,o-,oo,,ud [ e,o_.u.,.O>,oou°,d
A,./-/~s
_~_/LA//
r,
.
i- Z..o.. e l'' 'r"
le'-'°"
*>'°"
I
I
Fig. 1. (A) Sampling stations, (B) Total hydrocarbons O~gtg), (C) Coprostanol (#g/g), and (D) Coprostanol (% of total sterols) in sediments of the canals and lagoon of Venice. Italy.
in this area. The present study was undertaken to investigate the current state of health of sediments and organisms from the canals and Lagoon of Venice based upon a survey of several different types of pollutants including petroleum hydrocarbons, pesticides, polychlorinated biphenyls, and coprostanol, a fecal sterol indicative of sewage discharge.
METHODS Surface sediments (top 5 cm) were collected from 25 stations in the canals, lagoon, and coastal waters of Venice, Italy during September and October, 1985 (Fig. !). [Mussels (Mytilus gallprovincialis) were also collected and similarly analyzed from 20 of these
Coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments
759
Table 1. Data for organic and inorganic parameters measured in sediments from the canals and lagoon of Venice, Italy Station 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
% H 2 0 %CO 3 %OC 29.6 39.9 50.8 55.8 41.9 30.5 42.9 31.3 38.0 22.1 37.8 25.2 25.9 31.7 46.7 37.6 30.2 48.0 50.1 18.3 49.9 52.5 44.8 51.7 47.2
56.5 51.7 44.7 47.8 52.4 54.9 55.0 48.6 52.5 68.3 55.8 63.5 61.2 50.7 48.3 45.8 48.0 43.2 37.0 64.0 39.6 48.7 33.6 42.7 36.2
0.9 2.2 2.9 2.0 1.4 1.3 1.6 1.1 1.3 0.3 1.4 0.6 0.5 1.3 2.0 2.2 0.7 2.1 2.3 0.1 2.0 3.3 3.3 3.1 4.6
XCOP (/zg/g)
%COP
EHC (/*gig)
EPCB (ng/g)
Y-DDT (ng/g)
1.7 10.4 2.2 3.6 0.9 1.0 1.5 2.2 2.8 1.0 2.8 0.8 1.7 2.9 3.1 8.7 0.5 1.8 2.3 0.2 0.3 40.9 13.6 20.5 4.4
18 33 13 15 8 10 9 16 15 19 15 7 14 15 22 28 7 11 8 10 5 39 42 38 29
84 129 138 78 28 93 39 48 27 6 68 14 64 35 90 250 5 40 89 3 228 302 115 66 391
128 41 259 49 140 744 55 306 119 113 277 12 20 190 187 230 9 41 297 5 152 305 350 292 448
16 4 19 4 5 105 5 32 10 3 66 2 3 22 12 21 1 3 6 2 8 28 120 69 79
EHCH (ng/g)
I;HCB (ng/g)
0.3 <0.1 0.3 0.1 0.2 0.2 0.4 0.1 0.1 <0.1 0.8 0.3 0.7 2.1 0.6 2.1 0.1 0.3 0.8 0.2 0.8 0.1 <0.1 0.1 0.5
1.9 0.9 3.5 6.5 4.0 2.8 1.2 1.0 0.7 0.1 0.8 0.1 0.2 0.8 2.8 1.9 2.4 13.0 224.0 0.2 66.0 3.5 2.7 7.8 3.4
Abbreviations: %CO 3 = percent total carbonates, %OC = percent organic carbon, ECOP = total coprostanol, %COP = coprostanol as percentage of total sterols, ~ H C = total hydrocarbons, ZPCB = total polychlorinated biphenyls, ' r D D T = total DDT's, ~ H C H = total hexachlorocyclohexane, XHCB = total hexachlorobenzene.
stations. These results are being reported elsewhere.] After addition of internal standards (5~-androstane, o-terphenyl, and 5~-androstanol), approximately 20g (dry weight) of each sediment was Soxhlet extracted and saponified using 2:1 0.5N Methanolic KOH:benzene (Van Vleet et al., 1986). Extracts were dried over anhydrous sodium sulfate, evaporated under vacuum to -~ 1 ml, and processed by silica gel-alumina column chromatography (Reinhardt and Van Vleet, 1986) to isolate the saturated (aliphatic; F1) hydrocarbons, unsaturated (aromatic; F2) hydrocarbons, and total sterols (F3). Individual column eluates were analyzed by high resolution gas chromatography (Hewlett-Packard 5580A GC) using a 30 m DB-5 fused silica column with hydrogen as a carrier gas. Oven temperature programming conditions were as follows: hydrocarbons (FI and F2)--100-280°C at 6°Cmin-~; sterols--180-280°C at 3°C min-1. Individual compounds were corrected for detector response factors and integrated using a Hewlett-Packard data processor. Structural confirmation and polycyclic aromatic hydrocarbon (PAH) homolog distributions were determined by combined high resolution gas chromatography-mass spectrometry (GCMS) using a Hewlett-Packard 5992B-GCMS system under conditions similar to those employed by GC. Extraction of chlorinated hydrocarbons was accomplished by refluxing ~- 50 g of wet sediment in a Soxhlet apparatus for 8 h firstly with acetonitrile then with hexane, using 2,4,5-trichloro-biphenyl as an internal standard. Combined extracts were partitioned against pesticide-free water and the aqueous phase was extracted twice more with 50 ml portions O.G. 13/4-6--M
of hexane. Combined extracts were dried over anhydrous sodium sulfate, evaporated under vacuum to I ml, shaken with concentrated sulfuric acid to remove co-extracted substances (Murphy, 1972), and then shaken with mercury to bind sulfur compounds which interfere in the GC analysis. Extracts were fractioned into classes of chlorinated hydrocarbons by elution from a silica gel micro-column (Palmork and Villeneuve, 1980) and concentrated to I ml for gas chromatographic analysis using a Carlo Erba FV2351 electron capture GC. Identity of organochlorines was determined from their retention times on two GLC columns (2 m x 4 mm i.d.; 5% DC 200 on Gas Chrom Q BW-DMCS and 5% QF-I on Chromosorb W AW-DMCS). Quantification was based on peak-height measurement and comparison to responses of reference standards (HCB, HCH, DDT's, and Aroclors 1254 and 1260). Organic carbon was analyzed by the chromate digestion method of FAO (1975). Total carbonates (CaCO3 + MgCO3) were measured by a gas-volumetric method in which the volume of CO2 released from 1 g of sediment upon acidification with 25 ml of 1.2 N HCI is measured manometrically and compared to standard CaCO3 gas release curves. Moisture content was determined after drying a weighed subsample of each sediment to constant weight at 65°C. RESULTS AND DISCUSSION
Data obtained from all organic carbon, carbonate, and lipid analyses are reported in Table 1 and plotted in Figs 1 and 2. Organic carbon values in the lagoon
760
E.S. VAN VLEETet
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A
(?C ; ~ I
,°:1°oo I =:70:001" l
Fig. 2. (A) Total DDT, (B) Total PCB's, (C) HCB, and (D) HCH in sediments of the canals and lagoon of Venice, Italy. All concentrations are in ng/g. range from 0.3 to 4.6% with highest values ( > 3 % ) being observed in the interior canals of the city (Sta. 22-25) and the lowest value being observed at the control station (Sta. 20) located = 14 km outside of the lagoon in the Northern Adriatic Sea. Most other organic carbon values in the lagoon ranged from about 0.3-2.9% and were inversely correlated with carbonate contents of the sediments (correlation
coefficient r = -0.81, Table 2). Unusually high accumulation of organic carbon was not observed in this area. The fecal sterol, coprostanol (5fl-cholestan-3fl-ol), has been used in many studies to investigate sewage discharge (Hatcher and McGillivary, 1979; Boehm, 1983; Pierce and Brown, 1984; Sherwin, 1988; and many others). Since coprostanol is produced almost
Coprostanol, petroleum hydrocarbons, and chlorinated hydrocarbons in sediments
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Table 2. Correlationeoeflicients(r) among organic and inorganicparametersmeasured in the present study %H20 %C03 %OC HC PCB DDT HCH HCB COP %COP %H20 1.00 %CO3 -0.77 1.00 %OC 0.81 -0.81 1.00 HC 0.50 -0.55 0.78 1.00 PCB 0.21 -0.38 0.47 0.45 1.00 DDT 0.15 -0.39 0.49 0.33 0.82 1.00 HCH -0.05 -0.12 0.01 0.22 0.05 -0.07 1.00 HCB 0.30 -0.40 0.14 0.07 0.12 -0.14 0.15 1.00 COP 0.42 -0.26 0.54 0.48 0.23 0.27 -0.13 -0.09 1.00 %COP 0.31 -0.34 0.63 0.48 0.29 0.51 -0.08 -0.24 0.77 1.00 Abbreviationsas in Table 1.
exclusively in the intestines of mammals (including man) by enteric reduction of cholesterol, the presence of coprostanol is considered to be a reliable indicator of municipal waste discharge. Figures 1C and 1D show the sedimentary concentrations of coprostanol (rig/g) and the abundance of coprostanol as percent of total sterols. In areas with the highest concentrations of coprostanol, this compound generally makes up a greater percentage of total sterols (r = 0.77, Table 2). These areas most commonly represent interior canals with limited water circulation and tidal flushing. Coprostanol concentrations range from 0.2 #g/g at the Northern Adriatic station (Sta. 20) to 40.9/~g/g in the interior canals. Away from the interior canals, coprostanol concentrations averaged 1.8 + 1.0/~g/g (n = 18) while interior canals averaged 16.4 _ 13.1/zg/g (n = 6). While coprostanol concentrations in areas away from interior canals are comparable to many other estuaries around the world, concentrations in the interior canals are up to an order of magnitude higher than most other areas (Goodfellow et al., 1977; Hatcher and McGillivary, 1979; Escalona et al., 1980; Sherwin, 1988). High coprostanol concentrations in these canals provide an indicator of potential public health problems associated with other contaminants (such as pathogenic bacteria, etc.) resulting from raw sewage discharge. Sedimentary hydrocarbon concentrations ranged from 2.7/~g/g in the Northern Adriatic to 391/~g/g in the interior canals (Table 1, Fig. 1B). Although high concentrations were more widespread than for coprostanol, hydrocarbon contamination was only weakly correlated with coprostanol concentrations (r = 0.48, Table 2). Nonetheless, Fig. 1 shows that "hotspots" for hydrocarbons and coprostanol occur in the same general vicinities. Hydrocarbons are also concentrated around the industrial zone of Porto Marghera. Stations taken in interior canals and at Porto Marghera averaged 196_ 115 #g/g (n = 8) while other areas of the lagoon averaged 50 + 36/~ g/g (n = 16). Although gas chromatograms from most areas contained 70-80% unresolved hydrocarbon components, the F1 resolved peaks did not directly resemble petroleum inputs. Resolved alkanes showed significant contributions from nCl7-nC2! and nC25-nC3! with slight odd carbon predominances (Table l). F2 (aromatic) hydrocarbon fractions, how-
ever, were strongly dominated by unsubstituted PAH components, specifically by fluoranthene, pyrene, phenanthrene and benz(a)anthracene/chrysene (the latter two were not individually quantititated). In general, the ratio of the unsubstituted parent PAH compound to the total C1423 alkylated homologs was >1. Based upon the high percentage of unresolved components, low continuous n-alkane abundance, and dominance of unsubstituted PAH homologs in the F2 fraction, we suggest that hydrocarbons in both canal and lagoon sediments result from significantly degraded products of fossil fuel combustion rather than direct petroleum input. Since the city of Venice primarily uses natural gas for home heating fuel (Getti and Batisse, 1983), sedimentary hydrocarbons are more likely to result from inefficient burning of fuel oils by the extensive boat traffic in the Lagoon or by the industries in Porto Marghera. Hydrocarbon concentrations are well correlated with total organic carbon contents (r = 0.78, Table 2) in the sediments, indicating that sedimentary hydrocarbon distributions may also reflect extensive microbial reworking of organic matter discharged directly to the canals and lagoon. Fossato and coworkers (Fossato and Sivero, 1974; Fossato and Dolci, 1976, 1977; Fossato et al., 1979) have analyzed mussels from the Lagoon of Venice and have attributed hydrocarbon accumulation in the mussels to petroleum inputs. In the present study, hydrocarbons extracted from mussels much more clearly resembled direct petroleum inputs (n-alkanes continuous with odd/even ratio ~- 1.0) than did the sedimentary hydrocarbons. This observation suggests that petroleum contaminants in the lagoon may be taken up by mussels, but are probably degraded or carried away by tidal flushing prior to being permanently deposited in the sediments. Chlorinated hydrocarbons that were analyzed in the sediments included total DDT (dichlorodiphenyltrichloroethane), total PCB's (polycholorinated biphenyls), HCH (hexachlorocyclohexane), and HCB (hexachlorobenzene). For decades, PCB's and HCB have been used for a variety of industrial applications while DDT and HCH have been used as pesticides and fungicides in agriculture. Since 1970, the use of HCH has been greatly limited in Italy and by 1978 its use was completely banned by Italian regulations. At
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E.S. VAN VLEETet al.
the same time, the use of PCB's was restricted to non-dispersive systems. These highly toxic compounds are extremely resistant to chemical and biological degradation and may persist in the environment for several decades. Table 1 and Fig. 2 show the concentrations and distributions of these components around the city and lagoon of Venice. Distribution patterns for the various chlorinated hydrocarbons differ and are dependent upon varying local inputs. Total DDT and PCB's show distribution patterns similar to coprostanol and total hydrocarbons, being concentrated mainly in sediments of the interior canals. High PCB concentrations appear to be much more widespread and are also found at Porto Marghera. For PCB's and DDT's, an area of relatively high concentration was also observed at Sta. 6 near the island of Giudecca, and was probably due to the former presence of a shipyard in this area. Total DDT/total PCB concentration ratios are <0.5 at all stations, and are similar to values reported earlier for DDT and PCB's in mussels and sediments collected in other areas of the lagoon (Fossato and Craboledda, 1979; Fossato, 1982). Although this may indicate a higher input of PCB's to the environment, it may also reflect different biochemical pathways of these compounds in the lagoon. Although DDT and PCB concentrations are strongly correlated with each other (r = 0.82, Table 2), they are only weakly correlated with hydrocarbon or coprostanol concentrations (r =0.23-0.45). Nonetheless, distribution patterns are basically similar for all of these compounds. Distribution patterns of HCB and HCH are strikingly different than for the other compounds (Fig. 2). Interior canals appear to have relatively low concentrations compared with some of the other areas. HCB is concentrated primarily near Porto Marghera and may be associated with release by the chemical industry in this area. HCH shows relatively high concentrations near the northern portion of Venice and probably reflects agricultural inputs, although the exact source is unknown. Table 2 confirms that HCH and HCB are very poorly correlated with any of the other organic parameters measured (r = 0.01-0.19). In summary, we can see that "hotspots" for hydrocarbons, fecal sterols, and chlorinated hydrocarbons occur primarily in interior canals of Venice and the industrial area of Porto Marghera. Although these "hotspots" show elevated concentrations relative to other areas of the Lagoon, concentrations are not necessarily higher than in other coastal bays and estuaries around the world. An exception is the fecal sterol, coprostanol, which shows up to an order of magnitude higher concentration relative to sediments from most other marine environments. These high concentrations result primarily from the input of untreated waste into the interior canals of Venice. It appears that flushing of the canals and lagoon by
tidal currents limits the accumulation of pollutants in most areas studied, although dredging of the interior canals would significantly reduce pollutant concentrations in these areas. If flood gates are constructed that restrict tidal circulation in the lagoon, accumulation of pollutants could dramatically increase. Acknowledgements--Financial support was provided by the
Gladys Krieble Delmas Foundation. Investigators from the University of South Florida greatly appreciate the hospitality and assistance provided by the Istituto di Biologia del Mare in Venice. REFERENCES
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